Crop Tech

To the rescue
Peter Scharf hopes the soggy 2009 growing season will result in a lesson learned regarding nitrogen (N) deficiency in corn.
"Producers get discouraged and think it's too late when they see deficiency symptoms in their corn fields,” says the University of
Missouri fertility specialist. "My research suggests that corn can respond to N effectively at surprisingly late application timings.”
Up until 4' in height, Scharf says, average corn yield from a single application did not depend on timing. "In other words, a single application of N gave the same yield on average if it was applied at planting, when corn was 2' tall or when corn was 4' tall,” he notes. He says this finding is also backed by extensive data from Nebraska, Minnesota, Iowa and Oklahoma.

"Even at tasselling, yield was still above 90% of its full potential if rescue N was applied at that stage.”

Limited data suggests that a profitable yield response is likely to happen until two weeks after tassels emerge in corn that is experiencing significant N stress.

"My conclusion is that the logistics of getting the N applied is a much greater obstacle than the ability of the crop to use the N,” Scharf adds. High-clearance applicators, airplanes and pivot irrigation systems can all be effective ways to deliver N to stressed corn. Among these options, Scharf says, sprayers are the most widely available option in Missouri, but many are not plumbed to accommodate drop nozzles between rows.

"Lack of preparation is the biggest obstacle to making rescue N applications. After the past two years, it's my firm belief that every producer and every retail organization needs to have a plan for making rescue N applications in place before the season starts,” he says.

Nitrogen Deficient Hybrids
It's elementary—modern corn production takes nitrogen (N). Still, says Greg Luce, technical product manager for Pioneer Hi-Bred, developing corn hybrids that require less of the necessary element is a very important target for his company.

"Years of nitrogen testing have shown us that hybrids typically respond to nitrogen similarly,” Luce says. "We're working hard to test hybrids in nitrogen-deficient conditions to determine if there are native differences in performance at low nitrogen levels. We are also looking at transgenic events that may lead to hybrids using nitrogen more efficiently.”

Pioneer research has shown that hybrids within the same maturity zone don't differ much with respect to N utilization. "Through extensive testing in low nitrogen levels, we do see some difference,” Luce says. For this research, scientists test hybrids in continuous corn blocks that are depleted of N for comparison purposes. "Rotation with legumes, such as soybeans, has been done for a reason, and soybeans do contribute to nitrogen the following year,” Luce notes.

Luce also believes there might be some connection between more N-efficient hybrids and drought tolerance. "Nitrogen moves with water, and in a drought the corn plant typically ‘fires up' and expresses signs of nitrogen deficiency,” he says. However, he cautions that "nitrogen-use efficiency and drought tolerance are very complex traits and there are many factors to consider that are unique to both.
"Pioneer is much further along in the ongoing development of more drought-tolerant corn, which has been a key target for over 50 years,” Luce says.

Pioneer is testing transgenic events that have shown multiple years of yield advantage in reduced-N environments. "It may be a decade before more nitrogen-efficient products are marketed, but there are some very promising things coming to help growers and the environment with regard to this kind of technology,” Luce says.

Can Corn Fix its Own Nitrogen?
The Holy Grail for the corn industry is a hybrid that would fix its own nitrogen. University of Illinois agricultural engineer Kaustubh Bhalerao believes research in synthetic biology may be the key to "teaching” corn to do just that.

"We now understand enough about how genes work and how proteins are produced that we can actually think about reprogramming how living cells work,” he says.

Synthetic biology is a new area of research that combines science and engineering in order to design and build, or "synthesize,” novel biological functions and systems.

Bhalerao is leading a multidisciplinary research initiative with collaborators from the University of California, San Francisco; Stanford University; University of Cambridge and Newcastle University aimed at building systems that enable bacteria to spatially organize, communicate with and control plant cells. The research is funded through a grant of about $2 million from the U.S. National Science Foundation and the United Kingdom's Engineering and Physical Sciences Research Council.

"We've developed the equivalent of an amplifier inside bacteria,” Bhalerao says. "The bacteria sense the presence of an amino acid in their environment and produce a protein in response. A positive feedback mechanism in the gene circuit amplifies the production of that protein. By using bacterial amplifiers, the systems become more sensitive.”

A specific application being investigated is the design of a system that enables nitrogen-fixing bacteria to communicate with the root systems of corn plants.

Soybean fixes its own nitrogen by sending a message to a bacterium that encourages it to colonize in the plant's roots. Once the right environment has developed, the bacteria will start fixing nitrogen for that plant.

"Why don't we teach corn how to do this?” Bhalerao asks. He says synthetic biologists have made biosensors to assist with other activities, such as nuclear mining of uranium and the detection of unexploded land mines in the soil.

"This type of technology allows us to think about interesting, novel solutions to major concerns, such as how we can feed more people or how we can produce more drinking water,” Bhalerao says.